810 fllE ENTOMOLOGIST. 



melanic varieties in those districts. The cases of Antphidasys 

 hctularia v. douhlcdayaria and Hybernia progemmaria v. infuscata 

 have been frequently brought forward, but a more precise array 

 of statistics on the subject is desirable. 



Toward the close of Mr. Sharp's paper he refers to Lord 

 Walsingham's suggestion that melanism would be advantageous 

 to insects in cold and sunless climates, by securing increased 

 absorption of heat rays. The theory appears very plausible, as 

 Mr. Sharp admits, and based on more tangible grounds than 

 some others. But there are some facts which should be con- 

 sidered when estimating its claims to acceptance. Though it is 

 easy to conceive that in a former epoch, mountain regions and 

 many countries in high latitudes, may have suffered from a defect 

 of sunshine, producing conditions which Lord Walsingham's 

 theory would apply to, yet this seems ver}' far from being the case 

 now, either in Iceland, Scandinavia, or the Central European Alps, 

 where the summers are very hot and sunny compared with those of 

 the British Islands; so that we should expect to find melanism, if 

 of modern origin, chiefly notable in Ireland and Scotland, and in 

 a less degree in the rest of Great Britain. And what is really 

 the fact as to the distribution of dark varieties in Alpine and 

 Arctic regions ? We should bear in mind that the theory in 

 question seems only applicable to Diurnal Lepidoptera. As 

 this includes only a small proportion of the Heterocera, let us 

 take the case of the Bhopalocera only. I do not know that any 

 portion of these in the British Islands, are remarkable for 

 melanochroic tendencies. And further, it will, I think, be found 

 that in case of species of wide range, in most instances a 

 northerly latitude produces a tendency to pallid coloration, a 

 loss of metallic lustre in several genera, such as Cooionympha, 

 ArgynniSfSLudEuchloe: and an indefinite delineation: — phenomena 

 indicating an inferior degree of vitality. Moreover, in the case 

 of distinctively Northern or Alpine species, such as certain of the 

 Pieridse and Coliidse, and the genera of Parnassius and CEneis, 

 we do not find dark coloration to be the rule, excepting in the 

 genus Erehia. Among the latter, however, we do not find any 

 approximation to a gradation of tone, corresponding to the 

 altitude or zone which they affect. Though one or two species 

 which frequent the highest summits are extremely dark, those 

 which are confined to the lowest region are only a shade lighter, 

 paler species occurring in the intermediate zones. In the 

 Pieridse it is true that the var. bryonm of P. napi appears to be 

 an instance in favour of Lord Walsingham's theory ; but against 

 this we have P. callidice, frequenting a much higher level, 

 which shows no similar peculiarity. The Arctic and Alpine 

 Coliidse, both species and varieties, are paler than those of the 

 warmer regions, with but a single exception as far as I know ; 

 and in the genera of Argynnis and MeliUea similar phenomena are 



